This invention relates to piston and cylinder assemblies, particularly, but not exclusively for internal combustion engines or reciprocating compressors, in which the piston is made of aluminium alloy.
Aluminium-base alloys suitable for use in the manufacture of pistons and other motor parts are described in British Pat. Nos. 334,656 and 480,499, in U.S. Pat. No. 2,357,450 and in French Pat. No. 998,474.
An object of the present invention is to provide a piston and cylinder assembly of which not only is the piston made of aluminium alloy, but the cylinder wall, forming part of the cylinder block or of a cylinder liner, is also made of aluminium alloy and in which the aluminium alloy piston can run directly on the aluminium alloy cylinder wall without the interposition therebetween of a permanent protective coating of another, e.g. harder, metal.
The problem of providing a suitable aluminium cylinder liner material in which to run an aluminium alloy piston has received considerable attention. For example, the Chevrolet Vega cylinder block is manufactured in a Reynolds Metals 17% silicon aluminium alloy, the running surface of the cylinder being given a special chemical etching treatment and the piston being iron-plated. It is also known to produce air-cooled aluminium alloy cylinders in 12% silicon aluminium alloy in which the running surface of the cylinder is coated with electroplated nickel and silicon carbide.
Rig tests using an aluminium alloy with a composition of 18.33% silicon; 1.48% nickel; 1.49% copper; 1.20% magnesium; 0.40% iron, after solution and precipitation heat treatment, running against a test bar of pseudo-eutectic aluminium alloy having a composition of 11.46% silicon; 1% nickel; 1.13% copper; 0.91% magnesium; 0.17% iron, after solution and precipitation heat treatment, resulted in seizure occurring between the two components.